[183523] in North American Network Operators' Group
RE: BGP advertise-best-external on RR
daemon@ATHENA.MIT.EDU (Jakob Heitz (jheitz))
Sat Sep 5 13:15:55 2015
X-Original-To: nanog@nanog.org
From: "Jakob Heitz (jheitz)" <jheitz@cisco.com>
To: "nanog@nanog.org" <nanog@nanog.org>
Date: Wed, 2 Sep 2015 18:38:42 +0000
Errors-To: nanog-bounces@nanog.org
If your network is such that only a handful of routers supply redundant pat=
hs, then you can set up iBGP sessions with those directly without going via=
route reflectors. You can have most routes going through reflectors and a =
few through direct BGP sessions. Not everything needs to go through route r=
eflectors. You can even do both: Have a router peer with a reflector as wel=
l as directly if you only need the redundant routes in a few places. You wi=
ll end up with duplicate routes, but that's not a show stopper. You can avo=
id duplicate routes with route maps. You can have multiple route reflectors=
with different cluster IDs that carry the redundant routes only. Clients c=
an peer with multiple clusters. Use route maps to avoid duplicate routes. T=
hese last things get complicated to manage, so I'd still go for add-path if=
at all possible.
--Jakob
> Message: 2
> Date: Tue, 1 Sep 2015 14:51:27 +0200
> From: Mohamed Kamal <mkamal@noor.net>
> To: Jeff Tantsura <jeff.tantsura@ericsson.com>, Diptanshu Singh
> <diptanshu.singh@gmail.com>
> Cc: NANOG <nanog@nanog.org>
> Subject: Re: BGP advertise-best-external on RR
> Message-ID: <55E59F4F.8010704@noor.net>
> Content-Type: text/plain; charset=3Dwindows-1252; format=3Dflowed
>=20
> Hi,
>=20
> Diverse-path will only send the second best path, and in my case I have
> three routes not two. In addition to that, every PE will have to peer
> with the RR via a second session (on the same RR, as I will not deploy a
> new standalone shadow RR) and this will increase the BGP sessions to the
> double.
>=20
> Add-path will have a network-wide IOS upgrade for this BGP capability to
> be supported which is not viable now.
>=20
> So, is there any other recommendation other than the internet VRF with
> different RDs solution?
>=20
> Regards,
>=20
> Mohamed Kamal
> Core Network Sr. Engineer
>=20
> On 8/25/2015 11:37 AM, Jeff Tantsura wrote:
> > Hi,
> >
> > In your case I?d recommend to use diverse path, due to its simplicity a=
nd
> > non disruptive deployment characteristics.
> > As you know - diverse path requires additional BGP session per addition=
al
> > (second, next, etc) path, in most cases not a problem, however mileage
> > might vary.
> >
> > To my memory, in Cisco land - it has only been implemented in IOS, not =
XR,
> > please check.
> >
> > Cheers,
> > Jeff
> >
> >
> >
> >
> > -----Original Message-----
> > From: Diptanshu Singh <diptanshu.singh@gmail.com>
> > Date: Monday, August 24, 2015 at 10:53 PM
> > To: Mohamed Kamal <mkamal@noor.net>
> > Cc: "nanog@nanog.org" <nanog@nanog.org>
> > Subject: Re: BGP advertise-best-external on RR
> >
> >> Yes . In the case of diverse path , shadow route reflector will be the
> >> one wherever you enable commands to trigger diverse path computation.
> >>
> >> Good thing with diverse path is that the RR-Clients don't have to have
> >> any support but bad thing is that it can only reflect One additional
> >> best-path( second best path ) .
> >>
> >> Sent from my iPhone
> >>
> >>> On Aug 24, 2015, at 2:31 PM, Mohamed Kamal <mkamal@noor.net> wrote:
> >>>
> >>> It's only supported on the 15.2(4)S and later not the SRE train. I
> >>> might consider an upgrade.
> >>>
> >>> One more question regarding this, can you configure the RR to be the
> >>> main and shadow RR?
> >>>
> >>> Mohamed Kamal
> >>> Core Network Sr. Engineer
> >>>
> >>>> On 8/24/2015 9:16 PM, Diptanshu Singh wrote:
> >>>> BGP Add-Path might be your friend . You can look at diverse-path as
> >>>> well .
> >
